[one-liner]: Mounting a SMB/CIFS Share as an Automount on CentOS/Fedora/RHEL

Background

Here’s a quick tip on how to automatically mount/unmount a SMB/CIFS Windows share on a CentOS/Fedora/RHEL server, when ever it’s accessed. This tip makes use of Linux’s automounter (autofs) & the mount (mount.cifs) command.

Manually Mounting

command template

Here’s two examples of the prototypical command for mounting a SMB/CIFS share.

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# example pattern #1
% mount -t cifs //[hostname]/[share] [local_mount_point] -o sec=[security_type],user=[username]
 
# example pattern #2
% mount.cifs //[hostname]/[share] [local_mount_point] -o sec=[security_type],user=[username]

examples

The following 2 examples show how to mount a SMB/CIFS share passing all the arguments (username, password, etc.) via a single command.

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# real example #1
% mount.cifs //192.168.1.5/mp3s /mnt/mp3s -o sec=ntlmv2,user=joe_user
 
# real example #2
% mount.cifs //192.168.1.5/mp3s /mnt/mp3s -o sec=ntlmv2,user=joe_user,domain=dom.local

Here’s a better method, where the username, password, etc. are stored in a separate file which is a little more secure.

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# real example #3
% mount.cifs //192.168.1.5/mp3s /mnt/mp3s -o credentials=/etc/secret1.txt,sec=ntlm
 
# /etc/secret1.txt
#    username=joe_user
#    password=joespasswd
 
# real example #4
% mount.cifs //192.168.1.5/mp3s /mnt/mp3s -o credentials=/etc/secret2.txt,sec=ntlm
 
# /etc/secret2.txt
#    username=joe_user
#    password=joespasswd
#    domain=dom.local

NOTE: You’ll want to make the credential files (secret1.txt, secret2.txt, etc.) chmod 600 to limit visibility, the password is stored in clear text!

In example #1 above, this particular server required the security method: sec=ntlmv2. The default security method is ntlm. Examples #3 & #4 show how the username/password credentials can be moved to a file for better security. NOTE: Regarding sec=… here are some other possible values.

• none attempt to connection as a null user (no name)
• krb5 Use Kerberos version 5 authentication
• krb5i Use Kerberos authentication and packet signing
• ntlm Use NTLM password hashing (default)
• ntlmi Use NTLM password hashing with signing (if /proc/fs/cifs/PacketSigningEnabled on or if server requires signing also can be the default)
• ntlmv2 Use NTLMv2 password hashing
• ntlmv2i Use NTLMv2 password hashing with packet signing

Automounting

Automounting (autofs) provides the ability for resources to be mounted/unmounted based on whether they’re being used. After a period of inactivity, say 60 seconds, the automounter daemon wil unmount unused mounts. With a little work we can make it so that SMB/CIFS shares can be automounted as well. First you’ll want to make sure that autofs and samba are installed.

setup

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# automounter
% yum install autofs
 
# samba (client)
% yum install samba-client samba-common

Next you’ll want to add an entry to the file /etc/auto.master, like so:

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# file: /etc/auto.master
# ...
# ...
/mnt/cifs_share	/etc/auto.cifs	--timeout=600 --ghost

Now we’ll need to create the mount point:

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% mkdir /mnt/cifs_share

… and now create the file /etc/auto.cifs:

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share_data	-fstype=cifs,rw,noperm,credentials=/etc/credentials.txt	://192.168.1.11/share_data

And finally, create the credentials.txt file.

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# /etc/credentials.txt
username=joe_user
password=joespasswd

The last step is to startup the automounter service (/etc/init.d/autofs).

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% /etc/init.d/autofs start

testing automount

Once done you should now be able to cd to /mnt/cifs_share/share_data.

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% cd /mnt/cifs_share/share_data
 
% pwd
/mnt/cifs_share/share_data

You can confirm that the mount is being accessed correctly by checking out the list of active mounts:

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% mount
/dev/mapper/VolGroup00-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
//192.168.1.11/share_data on /mnt/cifs_share/share_data type cifs (rw,mand)

References

links

• HowTo Mout a CIFS Network Share
• Tips And Tricks – Windows Shares – CentOS Wiki
• Accessing Windows or Samba Shares using Autofs – howtoforge
• autofs with ghost option not showing wildcard mounts – serverfault

local copies

• HowTo Mout a CIFS Network Share
• Tips And Tricks – Windows Shares – CentOS Wiki

NOTE: For further details regarding my one-liner blog posts, check out my one-liner style guide primer.